ENG-1478: Port left sidebar to dual-readers + reactivity

[sid597]

https://www.loom.com/share/6258dfb98cd0424a9c1b3ef7794955c3

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Summary by CodeRabbit

Release Notes

• New Features

  • Added support for both global and per-section configuration of left sidebar folding behavior.
  • Enabled dynamic toggling of the left sidebar via feature flag.

• Improvements

  • Enhanced settings validation and synchronization across configuration systems to ensure consistency.

[linear]

ENG-1478 Port both global and personal left sidebar to dual-readers and leftsidebarview

[supabase]

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[sid597]

@coderabbitai full review

[coderabbitai]

✅ Actions performed

Full review triggered.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 6 additional findings.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR implements dual-read and dual-write support for left sidebar configuration. It adds a buildConfig helper to merge accessor-based values with legacy UID-backed settings, modifies useConfig to rebuild state from this merged config, wires dual-write support for folding state across global and per-section levels, and integrates feature flag handling into the extension lifecycle with proper cleanup.

Changes

Cohort / File(s)	Summary
Left Sidebar Config Logic apps/roam/src/components/LeftSidebarView.tsx	Introduces buildConfig helper merging accessor values with legacy UIDs; reworks useConfig to initialize/refresh from buildConfig; adds sectionIndex and isGlobal parameter propagation for dual-write folding state support via setGlobalSetting/setPersonalSetting; imports new accessor and type imports.
Settings Components Dual-Read apps/roam/src/components/settings/LeftSidebarGlobalSettings.tsx, apps/roam/src/components/settings/LeftSidebarPersonalSettings.tsx	Adds dual-read validation via getGlobalSetting and getPersonalSetting with type parameters; logs mismatches when flag is ON; uses legacy UID-backed data for CRUD operations.
Feature Flag and Lifecycle Integration apps/roam/src/components/settings/utils/pullWatchers.ts, apps/roam/src/index.ts	Introduces setLeftSidebarFlagHandler and leftSidebarFlagHandler callback registration; adds featureFlagHandler for "Enable left sidebar" flag; registers handler in index.ts to mount/unmount LeftSidebarView dynamically; captures and invokes cleanup from setupPullWatchOnSettingsPage in unload().

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• ENG-852 Render left sidebar based on fetched sections and settings #440: Adds LeftSidebarView and fold toggling foundation that this PR extends with accessor-based dual-write and buildConfig merging logic.
• ENG-1455: Dual-read from old-system settings and from blockprops #812: Implements the accessor functions (getGlobalSetting/getPersonalSetting) that this PR depends on for dual-read and dual-write operations.
• ENG-1188: prod: pull watchers for prop based settings #682: Related changes to pullWatchers and index.ts integration for feature flag handlers and settings page pull watcher cleanup.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: porting the left sidebar to dual-readers and adding reactivity, which aligns with the substantial changes across multiple components.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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